As the miniaturization of a semiconductor progresses, the size thereof in a horizontal direction is reduced, and the structure thereof in a vertical direction is also complicated. Therefore, there is a growing need for a technique that planarizes the surface of a semiconductor substrate (wafer) and facilitating processing. Among such planarization techniques, a chemical mechanical polishing (CMP) technique is particularly increasing in its importance. A substrate processing apparatus is used to perform various kinds of processing on a substrate (wafer) such as a semiconductor substrate. As an example of this substrate processing apparatus, a polishing apparatus that polishes a substrate such as a wafer by using the CMP technique can be cited (refer to Patent Literature 1).
The polishing apparatus using the CMP technique includes a polishing unit that performs polishing processing of a substrate, a cleaning unit that performs cleaning processing of the substrate, a drying unit that performs drying processing of the cleaned substrate, and a load/unload unit that transfers the substrate to the polishing unit and receiving the substrate subjected to the dying processing. Furthermore, the polishing apparatus includes a transfer unit that transfers the substrate between the polishing unit, the cleaning unit, and the load/unload unit. The polishing apparatus sequentially performs various kinds of processing such as polishing, cleaning and drying while transferring the substrate by the transfer unit.
An adsorption stage used in a cleaning tank or the like of the cleaning unit is provided with a vacuum adsorption line to vacuum-adsorb a substrate. Since the air and cleaning water remaining on the substrate are sucked from a through-hole for vacuum adsorption on the vacuum adsorption line when the substrate is vacuum-adsorbed, these moisture needs to be separated by an air-water separation tank. For this reason, the air-water separation tank is connected to the vacuum adsorption line (refer to Patent Literature 1).